1. Field of the Invention
The present invention relates to handling of elongated elements and, more particularly, pertains to a material-handling system which is suitable for use in sawmill operations.
2. Description of the Prior Art
A log entering a sawmill is initially sawed into lumber pieces (hereinafter referred to as cants) having flat and parallel top and bottom surfaces but unfinished longitudinal side surfaces or wanes. The wanes of a cant may be very irregular and are usually oblique to the top and bottom surfaces thereof. Accordingly, the cants have to be run through an edger to trim the wanes thereof such as to produce wood pieces having parallel side surfaces which are planar and perpendicular to the top and bottom surfaces thereof.
Conventional edgers generally comprise various transfer mechanisms which are adapted to transversally transport successive cants through a scanning station which is adapted to ascertain the profile of the cants. In accordance with calculations made on the basis of the profile data, the cants are conveyed and positioned on an infeed table of an edging station where the cants are longitudinally accelerated. Typically, the infeed table comprises a series of driven rollers disposed at regular intervals along the longitudinal axis of a frame for supporting and moving the cants and a series of overhead pressing rollers adapted to engage the top surface of the cants. The overhead pressing rollers are displaceable between inoperative and operative positions by means of hydraulic cylinders. Brackets are provided to connect the hydraulic cylinders to the overhead pressing rollers.
Although the conventional mechanisms used to transfer the cants from an intake station, through a scanning station and then onto an infeed table of an edging station perform satisfactorily, it has been found that there is a need for new and simpler transfer mechanisms which are adapted to enhance the productivity of an edging apparatus.
For instance, conventional cant transfer mechanisms do not allow to fill unwanted gaps between successive cants resulting from problems during the loading thereof on an entry conveyor of the edger.
Moreover, actual cant transfer mechanisms do not permit changing the speed of the production line according to the length of each incoming successive cant, although shorter cants require less time to be processed. Accordingly, this limitation results in a lost of productivity.
Another problem associated with the actual cant transfer mechanism is the premature wear of the hydraulic cylinders of the overhead pressing rollers of the edger infeed table. This is mostly attributable to the vibrations transmitted to the rollers when the same are in contact with the top surface of the cants. Furthermore, according to the above-described construction of the pressing rollers, the traveling speed of the rollers is limited, since relatively severe impacts of the rollers against the top surface of the cants can damage the cylinders.
It is therefore an aim of the present invention to provide an apparatus which is adapted to feed elongated elements.
It is also an aim of the present invention to provide such an apparatus which is adapted to feed elongated elements at a substantially uniform rate.
It is a further aim of the present invention to provide such an apparatus which is well adapted to cooperate with a scanning station and an edging station of a wood edger.
It is still an aim of the present invention to provide transfer mechanisms which are adapted to enhance the productivity of an edger.
It is still an aim of the present invention to provide a means for increasing the service life of an overhead pressing roller.
Therefore, in accordance with the present invention, there is provided an apparatus for feeding elongated elements at a substantially uniform rate comprising a frame having a longitudinal axis, multiple axially extending conveying means disposed in laterally spaced relationship on said frame means and adapted to be selectively driven at various speeds to move successive incoming transversally extending elongated elements along said longitudinal axis such as to provide a regular feeding rate, and means for controlling operation of said conveying means.
In a more specific construction, said multiple conveying means are independently and successively driven to convey one incoming elongated element at a time, thereby allowing the accumulation of one elongated element per conveying means at a delivery end of said apparatus.
In accordance with another general aspect of the present invention, there is provided an apparatus for transferring and orienting successive cants on an infeed table of an edging station. The apparatus comprises a frame having a longitudinal axis and at least two axially extending conveying means disposed in lateral spaced-apart relationship on said frame for moving successive incoming cants in a direction transversal to longitudinal axes thereof. Each conveying means includes first and second endless driving members. The first and second endless driving members are respectively provided with at least one first engaging means and with at least one second engaging means. The first and second engaging means are adapted to cooperate to convey successive incoming cants along said longitudinal axis of said frame. The first and second engaging means each have opposed pushing and abutment sides. The apparatus further comprises reversible motor means for selectively driving said first and second endless driving members of said conveying means in a forward direction and a backward direction, and control means adapted to control the operation of said conveying means such as to transport successive incoming cants to the infeed table of the edging station by alternately wedging the same between said pushing side of said first engaging means and said abutment side of said second engaging means, and between said pushing side of said second engaging means and said abutment side of said first engaging means.
In a further construction in accordance with the present invention, the pushing side of each said first and second engaging means is provided with compressible means, whereas said abutment side thereof is substantially rigid.
In accordance with a further aspect of the present invention, there is provided a method of transporting successive elongated elements transversally of respective longitudinal axes thereof. The method comprises the steps of: detecting a first incoming elongated element, positioning first engaging means adjacent a longitudinally extending upstream side of the first incoming elongated element, wedging the first incoming elongated element between said first engaging means and second engaging means located on a downstream side of the first incoming elongated element, moving said first and second engaging means in unison so as to transport said first incoming elongated element to a delivery location, moving said first and second engaging means away from said first incoming elongated element such as to position said first and second engaging means on the downstream and upstream sides of a second incoming elongated element, respectively, whereby said first and second engaging means alternately serve to push and retain the successive incoming elongated elements.
In accordance with a further aspect of the present invention there is provided an infeed table of an edging station adapted to cut away unfinished lengthwise extending wane surfaces of a cant to produce a dimensioned product as the cant is displaced therethrough along a prescribed edging path. The infeed table comprises infeed conveyor means for longitudinally displacing the cant into the edging station along the edging path, said infeed conveyor means including a supporting surface and a plurality of overhead roller pressing units, each said overhead roller pressing unit including first and second frame members pivotally mounted on a common pivot, said first frame member supporting a roller adapted to roll on the top surface of the cant, damping means disposed between said first and second frame members to absorb vibrations transmitted to said roller, and means for acting on said second frame member to displace said roller between an inoperative position wherein said roller is out of engagement with the cant and an operative position wherein said roller engages a top surface of the cant.
In accordance with a further aspect of the present invention there is provided an apparatus for feeding one element at a time, comprising frame means defining a longitudinal axis, a series of conveyors supported by said frame means and adapted to move incoming elements in a feeding direction parallel to said longitudinal axis, sensing means for detecting the space between successive incoming elements, and control means coupled to said sensing means and adapted to operate said conveyors to create a differential of speed between said conveyors such as to provide a desired spacing between the elements.
In accordance with a further aspect of the present invention there is provided a method for feeding one element at a time, wherein the elements are conveyed along a feeding direction by a series of conveyors, comprising the steps of: ascertaining the spacing between successive incoming elements, generating related spacing data, and on the basis of said spacing data, creating a differential of speed from one conveyor to another to provide a desired spacing between the elements.